/**
 * @param {number} n
 * @return {number}
 */
//通项公式f(n) = f(n-1)+f(n-2)
var climbStairs = function(n) {
  if(n<=2){
    return n
  }
  let dp = new Array()
  dp[1] = 1
  dp[2] = 2
  for(let i=3;i<=n;i++){
    dp[i] = dp[i-1]+dp[i-2]
  }
  return dp[n]
};

